Backup wellhead adapter

ABSTRACT

A backup wellhead adapter for a subsea wellhead that is positioned between an existing blowout preventer system and the wellhead. The adapter is a dual housing assembly that includes a primary housing longitudinally aligned over a secondary housing. The primary and secondary housings include lower bodies and upper necks that have identical diameters. During assembly, the existing primary blowout preventing system is initially connected to the neck on the primary housing. The lower body of the secondary housing is connected to a ram assembly connected to the wellhead connector or connected directly to the wellhead connector. When a blowout occurs, the primary housing is disconnected from the secondary housing to expose the upper neck of the secondary housing upon which a replacement primary blowout preventing system or cap may be attached.

This is a divisional patent application based on U.S. patent application(application Ser. No. 13/253,605) filed on Oct. 5, 2011 now U.S. Pat.No. 8,881,829 which is based on U.S. Provisional patent application(Application No. 61/390,745) filed on Oct. 7, 2010.

Notice is hereby given that the following patent document containsoriginal material which is subject to copyright protection. Thecopyright owner has no objection to the facsimile or digital downloadreproduction of all or part of the patent document, but otherwisereserves all copyrights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to blowout prevention systems for subseawellheads, and more particularly to blowout prevention systems thatserve as a backup or fail safe system to existing primary blowoutprevention systems.

2. Description of the Related Art

For subsea drilling operations, if the pressure of the formation fluidsexceeds the hydrostatic of the fluid in the well bore and the associatedsurface pressure applied, a blowout emergency may develop. Heretofore,the blowout emergency is managed by the operational personnel on theoffshore drilling unit using a subsea blowout prevention system(hereinafter referred to as ‘BOP system’) that is attached to thewellhead on the seafloor.

Federal regulations require that all offshore drilling operations use a‘BOP system’ that include different types of ram assemblies, annularseals, remote operated valves, a marine riser, diverter, tensioners, anda redundant control system managed from the drilling unit located on thesurface of the water.

A typical ‘BOP system’ connects to the top of the wellhead housing usinga cylindrical wellhead connector. The wellhead housing is found near theseabed and remains in place after the drilling unit has completed itsoperation and has been removed. The wellhead housing is designed towithstand all the stresses generated by the ‘BOP system’ and the marineriser running back to the drilling rig.

SUMMARY OF THE INVENTION

An important aspect of the following invention is the discovery thatexisting wellheads with ‘BOP systems’ can fail and that a backup blowoutpreventing systems that operates independent from the offshore drillingoperation or the primary ‘BOP system’ is needed.

Disclosed herein is a fail-safe, independently controlled and operatedbackup blowout prevention system for a subsea wellhead that also uses aprimary BOP system. The backup blowout prevention system which ispositioned between the primary BOP system and the wellhead allows thefluid flowing from the well to be shut off prior to reaching the primaryBOP system so that the primary BOP system may be repaired or replaced.In some instances, the backup prevention system may be cappedaltogether.

The backup blowout prevention system includes an independently operatedshear/blind ram assembly designed to attach to a standard wellheadconnector. The ram assembly includes a horizontally aligned main bodywith two opposing hydraulic ram units located at its opposite ends whichwhen activated are designed to shut off the flow of fluid through thetransversely aligned bore extending vertically through the main body.Perpendicularly aligned and mounted on opposite sides of the main bodyand aligned with the bore inside the main body is an upper neck and alower neck. Formed on the upper and lower necks are perpendicularlyaligned connection flanges. The connection flange on the lower neck isattached to the connection flange on the wellhead connector and theconnection flange on the upper neck is attached to the dual housingassembly.

The dual housing assembly includes an upper primary housinglongitudinally aligned and stacked over a lower secondary housing. Theprimary and secondary housings each include a wide, cylindrical lowerbody and a narrow, cylindrical upper neck that have the same diametersas a standard internal bore. Formed on the primary housing is aperpendicularly aligned flange surface that rests on a perpendicularlyaligned upper flange on the secondary housing. The secondary housingalso includes a lower flange that connects to the upper flange on theupper neck on the ram assembly. Each housing includes a longitudinallyaligned center internal bore that runs throughout the system.

The adjacent flanges on the ram assembly and the dual housing assemblyare connected together with suitable threaded bolts. When the primaryhousing or the primary BOP system is damaged, the ram assembly can beremotely activated to close the well. The primary housing may bedisconnected from the secondary housing thereby exposing the profile onthe neck on the secondary housing. A replacement BOP system may beattached to the secondary housing. In some instances, a cap may beattached to the secondary housing to stop the blowout.

The primary BOP system is under the control of personnel located on thedrilling unit while the operation of the ram assembly and cutting of thethreaded bolts used to hold the primary and second housing together arecontrolled remotely or operated by an independent remote operatedvehicle (ROV) vehicle. In the preferred embodiment, the control systemis located on the system to ensure a quick and independent response inemergency situations. Remote controls for this system can be providedusing multiple alternative options such as acoustics or ROV interface.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the system.

FIG. 2 is a sectional side elevation view of the primary housing.

FIG. 3 is a sectional side elevation view of the secondary housing

FIG. 4 is an illustration of the subsea backup blowout prevention systemshowing the replacement blowout prevention system in an installedposition.

FIG. 5 is an illustration of the subsea backup blowout prevention systemshowing a capping system in an installed position.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to the FIG. 1, there is shown a subsea backup blowoutprevention system 10 designed to be placed between the wellhead 90 andthe primary BOP 102. When damage occurs to the primary BOP system 102 orto the primary housing 60 used to connect the primary BOP system 102 tothe wellhead 90, the flow of fluids 105 from the wellhead 90 may bestopped and a partially concealed secondary housing 50 may be exposedand connected to a replacement primary BOP system 102′.

The system 10 includes a blind/shear ram assembly 20 mounted on awellhead connector 30 designed to connect to a wellhead 90. The wellheadconnector 30 includes a main body 32 with a longitudinally aligned neck34 attached or formed thereon. Attached or formed on the top edge of theneck 34 is a connection flange 36. Formed inside the main body 32 and inthe neck 34 is a continuous internal bore 38 that communicates with thewell bore 92 in the wellhead 90.

The ram assembly 20 is designed to selectively shear or close off thewellbore 92. The ram assembly 20 is an independently operatedshear/blind ram assembly designed to attach to the wellhead connector30. The ram assembly 20 includes a horizontally aligned main body 21with two opposing hydraulic ram units 22, 23 located at its oppositeends which when activated are designed to shut off the flow of fluids 92through the transversely aligned bore 24 extending through the main body21. Perpendicularly aligned and mounted on opposite sides of the mainbody 21 and aligned with the bore 24 is an upper neck 25 and a lowerneck 27. Formed on the upper and lower necks 25, 27 are perpendicularlyaligned connection flanges 26, 28, respectively. During assembly, theconnection flange 28 on the lower neck 27 is attached to the connectionflange 36 on the wellhead connector 30 and the connection flange 26 onthe upper neck 25 is attached to the dual housing assembly 40.

The dual housing assembly 40 is disposed between the ram assembly 20 andthe primary BOP system 102. The dual housing assembly 40 includes anupper primary housing 60 longitudinally aligned and stacked over a lowersecondary housing 50. As shown more clearly in FIGS. 2 and 3, thesecondary and primary housings 50, 60 are inverted T-shaped structures.Each housing 50, 60 includes a wide, cylindrical lower body 52, 62, anda narrow, cylindrical upper neck 54, 64, respectively, that have thesame diameters as the wellhead 90. Formed inside the lower body 62 ofthe primary housing 60 is a recessed cavity 66 that is sufficient indepth and diameter to receive the neck 54 on the secondary housing 50.Formed inside the upper neck 64 and communicating with the recessedcavity 66 is a longitudinally aligned bore 68. A longitudinally alignedbore 58 is formed inside the secondary housing 50 and extendscontinuously through the main body 52 and the upper neck 54.

Formed on the lower edge of the lower body 62 is a flange surface 63.Formed on the lower edge of the wide body 52 of the secondary housing 50is a lower flange surface 51 that connects to the upper flange 26 on theupper neck 25 on the ram assembly 20. The secondary housing 50 alsoincludes an upper flange surface 59 located along the top edge of thewide body 52 that is placed under and adjacent to the flange surface 63on the main body 62 on the primary housing 60 during assembly. Suitablethreaded bolts 85 are used to attach the lower flange surface 51 on thesecondary housing 50 to the upper connection flange 26 on the ramassembly 20 and suitable threaded bolts 85′ are used to attach the upperflange surface 59 to the lower flange surface 63.

As shown in FIG. 1, an optional guide funnel 80 may be longitudinallyaligned and extended around the upper neck 64 on the primary housing 60to facilitate attachment of the BOP system 102 to the primary housing60.

If an emergency condition occurs that results in damage to the primaryBOP system 102, the ram assembly 20 may be activated to shear or closeoff the wellbore 92. The threaded bolts 85′ used to connect the primaryhousing 60 to the secondary housing 50 are then cut or sheared withsuitable cutting tools (not shown) so that the primary housing 60 andthe primary BOP system 102 attached thereto may be removed. When theprimary housing 60 is removed, primary housing 60 also removed therebyexposing the neck 54 on the secondary housing 50. A new primary BOPsystem 102′ or capping system 104 may then be positioned over andattached to the neck 54 on the secondary housing 50.

The entire system 10 would be coupled to a control system that receivessignals from a remote station 110 to selectively activate the ramassembly 20. The system 10 may also include a remote operated vehicleintervention system that uses a hydraulic pump sub and hot stab andmanual high-torque threaded connectors to close the ram assembly 20.

Using the above described system 10, a method of replacing a blowoutpreventing system or capping a subsea drilling operation is providedthat includes the following steps:

-   -   a. creating a subsea wellhead;    -   b. selecting a backup blowout assembly that includes;        -   a wellhead connector configured to be attached to a            wellhead, a shear/blind ram assembly, a dual housing            assembly that includes an upper primary housing with an            exposed upper neck a lower secondary housing with a upper            neck covered by said primary housing, and a plurality of            connectors used to selectively connect said wellhead            connector to said wellhead, to selectively connect said ram            assembly to said wellhead connector, to selectively connect            said secondary housing to said ram assembly, and to            selectively connect said primary housing to said secondary            housing;    -   c. connecting said wellhead connector to said wellhead;    -   d. connecting said ram assembly to said wellhead connector;    -   e. connecting said dual housing assembly to said ram assembly;    -   f. attaching a primary blowout prevention assembly to said        primary housing on said dual housing assembly;    -   g. disconnecting said primary housing from said secondary        housing thereby exposing the upper neck of said secondary        housing; and,    -   h. connecting a replacement blowout prevention assembly or cap        to said upper neck on said secondary housing.

In compliance with the statute, the invention described herein has beendescribed in language more or less specific as to structural features.It should be understood however, that the invention is not limited tothe specific features shown, since the means and construction shown, iscomprised only of the preferred embodiments for putting the inventioninto effect. The invention is therefore claimed in any of its forms ormodifications within the legitimate and valid scope of the amendedclaims, appropriately interpreted in accordance with the doctrine ofequivalents.

We claim:
 1. A backup wellhead adapter, comprising: a. a primary housingwith a wide cylindrical lower body and an axially aligned narrowcylindrical neck, said lower body includes a recessed cavity, a lowerflange surface, and a longitudinally aligned bore; b. a plurality ofholes formed on said lower flange surface; c. a secondary housingstacked under said primary housing, said secondary housing includes awide cylindrical lower body and narrow, cylindrical upper neck, saidupper neck includes an upper flange surface and being the same diameteras said narrow, cylindrical neck on said primary housing enabling saidupper neck to be inserted into said recessed cavity in said primaryhousing and positioned below and adjacent to said lower flange surfaceon said primary housing, said lower body on said secondary housingincludes a lower edge with a laterally extending lower flange surfaceformed thereon that is parallel to said upper flange surface, saidsecondary body includes a longitudinally aligned bore that communicateswith said bore formed on said primary housing; d. a plurality holesformed on said upper flange surface on said secondary housing that arealigned with said holes on said lower flange on said lower body of saidprimary housing when said upper neck is inserted into said lower cavityformed on said primary housing; and, e. a first set of connectorsinserted into said holes formed on said lower flange surface on saidprimary housing and through said holes formed on said upper flange totemporarily connect said primary housing and said secondary housingtogether.